Breast sonography is not universally accepted as a screening technique. Differentiating masses as cystic or solid has been accepted as the traditional role of ultra sound in workup of breast masses. Further evolution of solid masses has been advised either by FNAC, large core percutaneous technique or excisional biopsy. Though well tolerated, these techniques do have some risk, induce patient discomfort and increase overall cost of health care.

With recent advances in technology, new hardware and software improvement and availability of Dynamic high resolution, real time ultrasound attempts are being made to evaluate solid breast masses further and differentiate benign from malignant lesions. Characteristic sonographic features of benign from malignant solid breast masses have been sought to decrease the large number of biopsies.

There is an overlap in sonographic findings between benign and malignant solid breast lesions. To be able to characterize all solid breast nodules is impossible. A reasonable goal is to identify subgroup of nodules that has low risk of being malignant so that option of follow up can be offered to the patient as an alternative to biopsy.

One has to rely upon an array of findings to evaluate solid breast lesions and call it benign or malignant. No characteristics are absolutely specific and it is impossible to distinguish all benign from all solid breast nodules using sonographic criteria. However sonographic criteria to be looked for are:

1. Shape and margin of the lesion: The shape of a mass can be described as round, oval, lobulated or irregular. Round and oval shapes are suggestive of benign masses. As long as there are fewer than three lobulations, the chances of malignancy is very less. The presence of greater than three lobulations is an indeterminate feature. Irregular shape is suspicious of malignancy. The margin of the lesion reflects the demarcation of the mass with surrounding tissue. It can be smooth, micro lobulated, irregular or spiculated. Gentle bilobulate or Tri lobulated margins are considered smooth. Presence of 2 or 3 gentle smooth, circumscribed and well-encapsulated lobulation strongly favours a benign etiology over cancer. The presence of many small lobulations, that is microlobulation, on surface of solid breast lesion is suspicious of malignancy. Numerous lobulations give the lesion a pleomorphic shape. Microlobulation are frequently associated with angular margins. All lesions with irregular shape, ill defined margins and / or spiculation irrespective of their internal structure, sound transmission and orientation are suspicious of malignancy. If such a lesion is accompanied by satellite lesions, enlarged lymph nodes, ingrowth into isoechoic lesion and surrounding tissues. Obtuse or acute pointed junctions are formed between the mass and surrounding tissues. Irregular margin or presence of spiculation indicate invasion of lesion into surrounding tissue. Sonographic spiculation consists of alternating hypoechoic and relatively hyperechoic lines radiating out from the nodule. Only hypoechoic or relatively hyperechoic spicules in skin or pectoralis fascia, is characterized as malignant

Width-AP dimension ratio: It has been suggested that benign masses tend to grow within the plane of the breast resulting in lesions that are relatively wide in length or width relative to their AP dimension. In contrast, the infiltration of malignant masses presumably allows them to grow perpendicular to the plane of the breast. Simple measurement of the lesion dimension has not proven useful as the sole means of differentiating benign from malignant lesions, but it one of the several discriminating features. Benign lesions, like fibroadenomas, which grow horizontally within tissue planes, have a greater width than AP dimension and are compressible, partially resulting into their oval shape. Most carcinomas traverse surrounding tissue planes, resulting in a more vertical orientation, are firm and much less compressible. In consideration with other criteria, Width to AP ratio greater than 1.4 is suggestive of benign lesion where as 1.4 or less characterized the malignant ones.

Echogenicity: The lesions can be anechoic, hypoechoic, isoechoic and hyperechoic. An anechoic lesion is a benign cyst, but a complex cyst with thickened wall is suspicious and if there is also presence of intracystic growth it is probably a malignant lesion. To comment on echogenicity of lesion, the surrounding fat lobules should be used as reference level. Markedly hypoechoic lesion with respect to fat is probably malignant. Hyperechogenicity of a lesion compared to surrounding fat is suggestive of its being benign.

Internal Echo pattern: A lesion can be homogeneous or heterogeneous. Homogeneity or Heterogeneity reflects the diversity of tissue components within the lesion. A heterogeneous lesion has a more chance of being malignant. However both benign as well as malignant lesions can demonstrate a homogeneous internal echo pattern

Shadowing: Many of the malignant lesions attenuate sound and cause shadowing behind all or part of the mass. It is common with scirrous cancers and less with highly cellular tumors. An abnormal area, heterogeneous, without a discrete mass, but with focal shadowing is suggestive of malignancy.

Calcifications: Most breast cancers are markedly hypoechoic. Calcifications seen within such a nodule are more likely to be malignant than benign.

Duct Extension: Malignant breast nodules sometimes have projections from the surface of the nodule, which extend radially within a duct toward the nipple (duct extension) and/or within ducts away from the nipple (branch pattern). All of these findings suggest that the nodule extends into or along the ductal system. This increases the chance that the nodule is malignant and has components of intraductal cancer.

To conclude, malignant features include an irregular shape; micro lobulated, ill-defined or spiculated margins, AP dimension greater than width; marked hypoechogenicity; attenuating distal echoes and punctate calcifications. Features typical of benignity are homogeneous hyperechogenicity; a thin echogenic capsule; ellipsoid shape and fewer than four lobulations. A lack of all malignant features plus a combination of benign features is required for the mass to be characterized as benign.[8]